When hauling loose flowing bulk commodity products, the amount of product that can be hauled by a vehicle is limited in a variety of ways, the following are the two most prevalent. In a high density load situation the amount of product being transported may be limited by the maximum weight capacity of the vehicle hauling the product. In a low density load situation the amount of product that may be transported is often limited by the cubic volume of the vehicle hauling the product.
There are two primary vehicles used for transporting commodities—rail cars and trailers. With rail cars, the commodities are generally loaded via openings on the top of the rail cars. The commodities are typically unloaded by tipping over the rail car or by opening doors on the bottom of the rail cars.
Unloading by tipping over the rail car often enables the rail car to haul commodities that would not unload well through doors on the bottom of the rail car, i.e. loads that bridge, don't flow well, freeze or stick to the interior require this method, in other cases faster unloading is the primary reason for using doors on the bottom of the rail cars. Tipping over the rail cars places forces on the sides of the rail cars that must be accounted for in the design of the rail car to prevent damage to the rail cars during the tipping process.
The maximum width and length of the rail cars and trailers is typically limited by law or regulation. Accordingly, it is generally not possible to increase the capacity of rail cars and trailers for low density loads by increasing the width and length of the rail cars and trailers.
While there are often restrictions on the height of rail cars and trailers, the rail cars and trailers are often manufactured shorter than the maximum allowed height due to the anticipated commodity that the vehicle was destined to haul. There have been various attempts to increase the capacity of rail cars and trailers by placing extensions on the top of the sides of the rail cars and trailers.
When attaching extensions to rail cars or trailers, it is often desirable for the extension to be removable so that they can be detached when not needed. Additionally, when attaching the rail car extensions to the rail car, it is often desirable to not use attachment mechanisms that could impact the structural integrity of the rail cars.